September 29, 2009

A self-cleaning hull

IN A COLUMN LAST MAY I was bemoaning the fact that boats have to be taken out of the water for antifouling at regular intervals. I asked: “Why can’t we make a bottom paint that acts like a fish’s scales or a dolphin’s skin? There must surely be a fortune waiting for someone who can invent a paint or some kind of skin like that, not only for yachts, of course, but also for large ships.”

Well, guess what. A reader who signs himself simply as “Dave” has now pointed me to a current article in the magazine New Scientist, issue 2727. It says that Rahul Ganguli, of Teledyne Scientific, in Thousand Oaks, California, is working on exactly that theory.

Ganguli’s idea is to cover the ship’s bottom with a layer of fine metal mesh. Underneath the mesh is a pattern of holes that exude a sticky sort of slime. The slime pools outside the mesh, making a viscous coating that steadily wears away, taking with it any kind of sea life that has managed to attach itself. The slime is constantly replaced by new secretions, apparently, though the article doesn’t say how.

Early tests in seawater tanks showed that after 11 days there was “a 100-fold cut” in the amount of bottom growth. I presume that means there was only one-hundredth of the normal marine growth you might expect in that time.

Ganguli apparently was inspired by a study of the skin of the long-finned pilot whale. That study was undertaken by Christoph Baum at the Hannover School of Veterinary Medicine in Germany. Baum’s team reported that the whale’s skin was criss-crossed with tiny canals filled with a gel that destroys proteins on the microscopic bacteria and algae which act as hosts to barnacles and other marine growth.

There is also some speculation that the proposed new coating will reduce drag, compared with that of a clean, smooth hull, so I guess the racers will be keen to try it out — at whatever cost — when Ganguli eventually gets all his ducks in a row.

Today’s ThoughtWe manipulate nature as if we were stuffing an Alsatian goose. We create new forms of energy; we make new elements; we kill crops; we wash brains. I can hear them in the dark sharpening their lasers.— Erwin Chargaff, professor of biological chemistry, Columbia University

Tailpiece“Does your dog have a pedigree?”“Sure does. If he could talk he wouldn’t be seen talking to either of us.”